The purpose of this study include examining the rates of specific psychiatric disorders in the first-degree relatives of adolescents with major depression (n=362), non-affective disorders (n=170), and no history of psychopathology (n=362). The probands will be drawn from the Oregon Adolescent Depression Project, a longitudinal epidemiological study of a large cohort of high school students. The following specific questions will be addressed: a) do the relatives of adolescents with major depression exhibit a higher rate of mood disorders than the relatives of normal controls; b) is the increased rate of mood disorders in relatives specific to adolescents with major depression, or is it also evident in adolescents with non-affective disorders; c) is there an increased rate of any non-mood disorders in the relatives of adolescents with major depression compared to the relatives of controls; and d) are important clinical characteristics such as age at onset, recurrence, and chronicity, also transmitted within families? The second aim is to test a comprehensive series of models of comorbidity between major depression and dysthymia, anxiety disorders, disruptive disorders, substance abuse in order to elucidate the nature of psychiatric comorbidity in adolescents. A third goal is to examine whether adult diagnostic criteria for major depression should be modified when applied to children and adolescents. Using familial aggregation of mood disorders as an external criterion we will determine whether, and how, the criteria for major depression should be modified for use with adolescents. Another goal is to compare the bottom-up with the top-down approach. Our study provides a unique opportunity to recover both designs from the same data set. A final goal is to use the extensive longitudinal data base from the OADP data set to develop and test theoretical models about the role of familial psychopathology in the development of depression in adolescents. Recent epidemiological studies indicate that mood disorders are more common among adolescents than had been thought, and that family history of mood disorders is one of the most potent risk factors for depression. Because of the limitations of the existing work in this area, a methodologically rigorous family study of adolescent depression such as the one being proposed would represent a valuable contribution. The proposed study offers important methodological advantages over previous work: a) specific diagnostic criteria and structured interviews used with both probands and relatives; b) relatives assessed directly; c) assessments of relatives conducted blind proband to diagnoses; d) diagnoses of relatives based on data from multiple sources; e) the probands were carefully evaluated on two separate occasions over a two- year period; f) both non-affective psychiatric and normal control groups will be employed so that the issues of increased risk and specificity of risk can both be addressed; g) sample sizes substantially larger than those employed in previous studies; h) a representative, community based sample will be employed.